Drainage of flat and low-pitch industrial roofs is complicated by the fact that they typically have low areas where rain water tends to pool. Pooled water, subject to frequent freeze/thaw cycles, not only stresses the roofing materials and the roof deck but also forms an environment where mosquitoes and other insects can breed and which nurtures the growth of mold and fungus.
In a typical industrial flat roof, roof drains are arrayed on 10 to 30 foot centers. Any low areas located between these roof drains need to be filled in to allow for proper drainage.
Moreover, in the case of a flat or low-pitch roof in which the roof abuts a parapet wall along at least a portion of the roof's outer perimeter, low areas can often be found next to the parapet wall, interspersed between individual parapet-penetrating openings at the roof/parapet wall interface. Fluidly connected via a scupper to a roof downspout as a rule, each parapet-penetrating opening is generally widely spaced apart from its respective nearest neighbors at the parapet wall.
In order to fill in these low areas and direct storm water toward the roof drains and/or the scuppers, one can utilize tapered roof insulation. Unfortunately, installing tapered roof insulation is a very costly, time-consuming process, entails extensive application of glues formulated from hazardous materials, and generates a tremendous amount of waste.
A less time and material-consuming construction process, as taught by Hamlin in U.S. patent application Ser. No. 13/385,400, is based on assembling an inflatable membrane. Each such membrane is equipped, prior to its being assembled on site, with an air valve permanently mounted on the membrane's outer surface. Not only must the inflatable membrane be sized and shaped to cover one of the roof's low spots (or a set of more or less contiguous low spots) and substantially overlap the latter's edges but also the membrane must be heat welded or otherwise joined to the existing roof covering or, alternately, a second membrane to form an airtight pocket in combination with the roof covering or the second membrane. Once properly constructed and then inflated, with the use of the air valve, the inflatable membrane, buoyed by this air pocket, protrudes upwardly, effectively elevating the covered low spot(s) and preventing water from puddling there during a rainstorm. Post construction, however, one must constantly maintain the air pocket in an inflated state or risk an unexpected collapses of the inflatable membrane onto the roof.